Orbital Sciences Corp.'s Antares rocket blasted off at 5 p.m. from Wallops Island - becoming the largest rocket to do so.

About 10 minutes after the launch on Virginia's Eastern Shore, Orbital of Dulles, Va., declared the test a success after observing a practice payload reach orbit and safely separate from the rocket.

The Sunday launch comes after two previous attempts were scrubbed. A data cord that was connected to the rocket's second stage came loose just minutes before the rocket was set to lift off Friday, and company officials said they were easily able to fix the problem. A second attempt Saturday was scrubbed because of wind.

The milestone set the stage for the Antares to launch a real cargo spacecraft, called Cygnus, on a demonstration mission to the station. That flight is tentatively planned in late June or early July.

"That's great news," space station commander Chris Hadfield radioed after being told of the successful launch. "Congratulations to all concerned, and that bodes well for all of our futures. Super."

The rocket's maiden flight came just more than five years after NASA selected Orbital to participate in a public-private partnership developing new rockets and spacecraft to resupply the station after the space shuttle's retirement.

The program already included SpaceX, whose Falcon 9 rocket and Dragon capsule last year became the first privately operated vehicles to reach the station and have now completed three successful visits.

NASA wants two commercial cargo suppliers up and running to ensure the station always has enough food and science experiments to support a crew of up to six.

NASA chief Charlie Bolden said the successful Antares launch also could help secure funding to fly astronauts commercially.

"Now we'll be able to go to the Hill and we'll be able to go other places and just say, 'OK, look what we just did. We've got two providers, we know how to do this stuff, and so have faith in American industry,' " Bolden said Sunday in congratulatory remarks to the launch team.

NASA is seeking $821 million next year to design and test private space taxis to carry astronauts under development by three companies - including SpaceX but not Orbital - with the goal of flights to the station by 2017.

SpaceX was awarded a $1.6 billion contract by NASA in 2006 to make a dozen missions to restock the space station. Orbital got into the mix in 2008 when it was awarded a $1.9 billion contract for eight deliveries.

SpaceX has connected with the space station three times.

In addition to testing the rocket systems, the mission dubbed "A-ONE" marked the first use of a new launch pad at Virginia's Mid-Atlantic Regional Spaceport.

After Orbital chose to launch from Wallops Island instead of Cape Canaveral, Fla., the state and NASA invested more than $140 million in the new pad and other facilities.

"That's a pretty good investment in the Eastern Shore here, and I think it has paid off," said Orbital executive Frank Culbertson, a former astronaut who directed the test flight.

Preliminary results showed the Antares and the pad performed well, though the launch did start a small brush fire that was not considered serious.

The launch team cheered as the rocket's first and second stages separated, then a payload fairing and finally the payload itself, placed in an orbit about 160 miles high.

The 8,400-pound "mass simulator," which had the shape and weight of a Cygnus spacecraft, will stay in orbit for about two weeks before being destroyed during re-entry through the atmosphere.

The dummy payload deployed four miniature satellites, including a trio powered by smartphones.

If the next demonstration mission goes well, Orbital would be cleared to fly the first of eight station resupply missions.

Orbital hopes Antares also will win launches of commercial and government satellites.

"We've proven we can do it," Culbertson said.

Orbital is under contract to deliver about 44,000 pounds of supplies to the space station and plans to make about two deliveries per year. Its cargo ship will carry about 4,400 pounds worth of supplies on each of its first three missions and 5,600 pounds on its last five.

Unlike the SpaceX's Dragon capsule, the Orbital cargo ship is not designed to return with experiments or other items from the space station. Instead, plans call for filling the Cygnus ship with garbage that would be incinerated with the vessel upon reentry into Earth's atmosphere. That's also what Russian, European and Japanese cargo ships do.

Orbital had hoped to begin its rocket launches under the commercial resupply program in 2011, but faced a series of delays. That included a delay in the completion of its launch pad at NASA's Wallops Flight Facility on the Virginia coast. That pad was built specifically for Orbital and is owned by the Virginia Commercial Space Flight Authority. The pad wasn't delivered to the company until October.

Sunday's launch drew scores of onlookers to Wallops Island's visitor center on the mainland several miles away, where people set up blankets and camp chairs near marshland to view the launch. Road signs also directed rocket launch fans to nearby Assateague Island, where the rocket launch could be seen from the beach.

For Mike Horocofsky of Rock Hall, Md., it was his third time making the drive down to the Virginia facility in hopes of seeing Antares lift off.

"I'd rather be doing this than anything else. It's just something I've enjoyed since I was a boy," Horocofsky said several hours before the launch, while setting up chairs for himself and his wife.